1. Field of the Invention
The present invention relates to a drive assembly system. More specifically, the present invention relates to a drive assembly which provides a scanning system with improved images.
2. Description of the Related Art
Radiation images, such as those in radiography and tomography, can be stored in conventional x-ray films or in storage layer radiation screens. Storage layer radiation screens have significant advantages of requiring lower levels of x-ray radiation to produce radiation images, and are reusable after an erasing and sterilization process. A typical storage layer radiation screen can be used for recording images of an object, such as a part of human body, exposed to radiation. The screen is then scanned with stimulating rays, such as a laser beam which causes the phosphors in the screen to emit light in proportion to the amount of radiation absorbed by the portion of the screen being scanned. The light emitted from the screen is then detected and converted into an electrical signal. The electrical signal is then used to reproduce the latent radiation image as a visible image.
During the scanning process, a portion of the storage radiation screen is illuminated with an excitation beam and emits light that is then collected by an image acquisition optics system. Generally, the excitation beam is directed toward the screen and scans across the screen line by line. The screen is induced by an excitation beam of a radiation source to luminesce pixel by pixel. Such scanning systems are described in U.S. Pat. Nos. 4,973,134, 4,543,479, 4,582,989, and 5,635,728. In particular, U.S. Pat. No. 5,635,728 describes a rotating scanner system to efficiently read multiple storage layer radiation screens. The carousel that holds multiple storage layer radiation screens is rotated about a rotational axis, and the screens adhered to the carousel are read by an image acquisition optical system positioned adjacent the carousel. As the carousel is rotated, the screen scanning system scans over a narrow line-shaped area of the screen perpendicular to the carousel""s rotational axis. The movement of the optics module in the direction parallel to the rotational axis of the carousel enables the screen scanner to scan over different narrow line-shaped areas of the screens as the carousel is rotated, thereby enabling the entire surface area of the screen to be scanned.
It is important for screen scanning systems to produce images read from the screens which have minimal artifacts and distortions generated by the scanning system. For example, artifacts such as lines or bands seriously detract from the perceived quality of the images. A need thus exists for devices and methods which can improve the image quality produced by such scanning systems.
A system is provided for scanning an object, the system comprising: a drive shaft having a proximal portion and a longitudinal axis; a motor including a motor shaft having a rotational axis, the motor serving to rotate the motor shaft about the rotational axis; a flexible joint coupling the drive shaft to the motor shaft by the proximal portion of the drive shaft, the flexible joint having a range of motion which allows the longitudinal axis of the drive shaft to move relative to the rotational axis of the motor shaft; and an object attached to the drive shaft which is movable along the longitudinal axis of the drive shaft in response to the drive shaft being rotated by the motor.
A system is also provided for scanning an object adjacent a rotatable drum, the system comprising: a drive shaft having a proximal portion and a longitudinal axis; a motor including a motor shaft having a rotational axis, the motor serving to rotate the motor shaft about the rotational axis; a flexible joint coupling the drive shaft to the motor shaft by the proximal portion of the drive shaft, the flexible joint having a range of motion which allows the longitudinal axis of the drive shaft to move relative to the rotational axis of the motor shaft; an object attached to the drive shaft which is movable along the longitudinal axis of the drive shaft in response to the drive shaft being rotated by the motor; and a drum positioned adjacent the object, the drum being rotatable about a rotational axis that is approximately parallel to the rotational axis of the motor shaft.
A system is also provided for scanning storage layer radiation screens, the system comprising: a drive shaft having a proximal portion and a longitudinal axis; a motor including a motor shaft having a rotational axis, the motor serving to rotate the motor shaft about the rotational axis; a flexible joint coupling the drive shaft to the motor shaft by the proximal portion of the drive shaft, the flexible joint having a range of motion which allows the longitudinal axis of the drive shaft to move relative to the rotational axis of the motor shaft; an image acquisition optical system attached to the drive shaft which is movable along the longitudinal axis of the drive shaft in response to the drive shaft being rotated by the motor; and a drum positioned adjacent the image acquisition optical system, the drum being capable of holding one or more storage layer radiation screens and rotatable about a rotational axis that is approximately parallel to the rotational axis of the motor shaft.
In each of the above systems, the flexible joint preferably has a range of motion which allows the longitudinal axis of the drive shaft to move at least about 1 degree relative to the rotational axis of the motor shaft, optionally at least 5 degrees and optionally at least 10 degrees. Also in each of the above systems, the drive shaft preferably rotates at a substantially constant angular velocity during a revolution of the motor shaft despite drag of the drive shaft varying across a rotation of the drive shaft.
In each of the above systems, the flexible joint is preferably longitudinally stiff, i.e., the motion of the flexible joint is such that the drive shaft is not displaced longitudinally by the motion of the flexible joint. This longitudinal motion of an object attached to the drive shaft due to lateral motion of the drive shaft.
In one variation of the above systems, the flexible joint includes a first hub for attaching the motor shaft to the joint and a second hub for attaching the drive shaft to the flexible joint, the first and second hubs being movable relative to each other. The first hub preferably has a first range of angular motion within the flexible joint and the second hub has a second, different range of angular motion within the flexible joint. These first and second ranges of angular motion are preferably in planes orthogonal to each other.
In the design of the flexible joint used in the above systems, the flexible joint may optionally include a first hub for attaching the motor shaft to the joint and a second hub for attaching the drive shaft to the flexible joint, the first and second hubs each including hub pins by which the hubs are attached to the flexible joint and about which the hubs have a range of angular motion. According to this design, the hub pins are preferably held under compression within journals in the flexible joint.